Such devices are known, for example, from European patent applications EP 1,205,125-A2 and EP 1,205,126-A1. In these known devices, the refillable unit may optionally comprise a filling valve, which can be in the form of an elastomeric flap that is integral with the body of the unit and can go from a closed configuration to a filling configuration under the effect of the pressure from the product coming from the container.